Vacuum switchgears utilized vacuum insulation with high insulation capability wherein switches are held in vacuum to thereby shorten insulation distance so that small sized switchgears are realized. Conventional vacuum switchgears are disclosed in patent document No. 1, for instance.
The patent document No. 1 discloses a vacuum switchgear comprising a main circuit switch, which comprises two pairs of main contacts for performing three positions of turn-on, breaking and disconnection, main circuit conductors for electrically connecting the two pairs of the main contacts, insulating rods for electrically insulatedly connecting the main circuit conductors with operators for the main circuit switches, and earth switches electrically connected to the main circuit switches disposed in vacuum chambers different from vacuum chambers for the main circuit switches, the main switch being accommodated in the vacuum chamber, which is molded with insulating resin coated with a conductive layer for earthing the vacuum chamber.
Patent document No. 1; JPA2007-14086